Effects of Mg doping on the superconducting properties of YBa2Cu3O7- deltaand La1.85Sr0.15CuO4systems

Abstract

The superconducting properties of YBa₂(Cu_1-xMg_x)₃O_{7- delta} (01.85Sr_0.15(Cu_1-xMg_x)O₄ (0c, with effects very similar to those observed in Zn-doped samples. An onset temperature of 79 K is found for YBCO at the maximum Mg solubility (x approximately=0.025). In LASCO, superconductivity is suppressed at x=0.03. Our results support the hypothesis that the detrimental effects on superconductivity of all non-magnetic dopants are similar, and are linked to the formation of a net magnetic moment in the CuO₂ plane. An estimation of the intergranular shielding current density J_s(T,H) in Mg:YBCO is also presented. Mg substitution affects the temperature dependence of J_s, but it does not change the variation induced by the application of an external DC magnetic field.